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MONOGASTRIC GI > 3b - Mastication, Swallowing and Esophagus > Flashcards

3b - Mastication, Swallowing and Esophagus Flashcards

1
Q

Mastication (chewing):

A

-mechanical breakdown of food in mouth

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2
Q

Incisors and mastication:

A

-procure food by tearing and scraping actions

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3
Q

Molars and mastication:

A

-grinding food into smaller particles
>carnivores: imperfectly grind food
>herbivores: spend more time masticating

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4
Q

What is the main purpose of mastication?

A

-break food into smaller particles to increase the SA for digestion
-mix food with saliva

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5
Q

What does mixing food with saliva ensure?

A

-adequate lubrication of food bolus for passage down esophagus

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6
Q

What is the epithelium that lines the mouth, tongue, pharynx and esophagus?

A

-stratified squamous epithelium
*can withstand mechanical trauma associated with mastication

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7
Q

Lingual papillae:

A

-aid in mastication
-increase SA for contact and friction between tongue and food
-divided into mechanical and gustatory
>those that are not associated with taste buds=mechanical

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8
Q

What are the 4 major papillae?

A

-filiform
-fungiform
-foliate
-circumvallate

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9
Q

Filiform:

A

-fine, small, cone-shaped papillae
-highly keratinized
-most numerous
-considered MECHANICAL (not associated with taste buds)

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10
Q

Fungiform:

A

-club shaped projections

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11
Q

Foliate:

A

-short vertical folds

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12
Q

Circumvallate:

A

-dome shaped

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13
Q

Carnivores and omnivores jaw movement of mastication:

A

-mainly in vertical plane producing a shearing action

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14
Q

Herbivores jaw movement of mastication:

A

-up and down
-lateral: mechanical grinding necessary to break down plant material
*upper jaw is wider than lower jaw:
*mastication only occurs on one side at a time

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15
Q

What are the teeth types?

A

-hypsodont
-brachydont

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16
Q

Hypsodont teeth:

A

-high-crowned teeth
-grow continuously
-herbivores and omnivores (eat fibrous material which needs to be ground)

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17
Q

Brachydont teeth:

A

-short, pointed teeth
-well suited for holding prey, tearing and shredding
-carnivores (and humans)
-begin to wear following emergence
*if enamel is worn, tooth begins to develop caries

18
Q

Saliva:

A

-produced by acinar glands located along mandible and upper jaw in most species
-contains digestive enzymes (amylase and lipase) in some species
>neonate: very low levels of amylase

19
Q

What are the functions of saliva and chewing?

A

-disruption of food into smaller particles
-formulation of bolus
-initiate of starch and lipid digestion
-facilitation of taste
-regulate food intake and ingestive behaviour
-cleansing mouth and selective antibacterial action
-neutralization of refluxed gastric contents
-mucosal growth and protection in rest of GI tract
-aid in vocalization

20
Q

Deglutition (swallowing):

A

-passage of food from mouth, through pharynx and esophagus to stomach
-starts as voluntary but becomes a reflex

21
Q

What are the voluntary movements in the mouth involved in deglutition?

A

-mouth and tongue bring food bolus to midline between togue and hard palate
>food is in contact with receptors in mucous membrane of posterior wall of pharynx

22
Q

What happens when food is in contact with receptors in mucous membrane of posterior wall of pharynx?

A

-receptors send afferent impulses along glossopharyngeal nerve (IX), vagus (X) and maxillary division of trigeminal nerve (V) to the swallowing centre in medulla
*from this point on, swallowing is involuntary (reflex)

23
Q

Swallow reflex: a series of coordinated actions:

A

-breathing stops momentarily
-soft palate is elevated, closing the pharyngeal opening (prevents food from entering internal openings of nostrils)
-togue is pressed against hard palate
-hyoid bone and larynx are pulled forward, glottis is pulled under epiglottis, blocking laryngeal opening
-all openings to pharynx are now closed
-upper esophageal sphincter relaxes to allow the bolus to enter the esophagus

24
Q

Timing of bolus transfer:

A
  1. Bolus in mouth
  2. Bolus moves through pharynx and UES (0.6s-1.1s)
  3. Bolus enters esophagus (1.1s)
25
Q

Esophagus:

A

-extends from pharynx to the stomach
*body serves as a relatively ‘simple’ conduit
-passes through thorax into abdomen
-myenteric plexus exists along the entire length

26
Q

What is the esophagus wall made of?

A

-muscular layer
-submucosa
-mucosa (stratified squamous epithelium)

27
Q

Esophagus anatomic considerations:

A

-UES
-striated
-smooth
-LES

28
Q

Esophagus muscles in different species:

A

-in most domestic animals=striated muscles
-horses, primates, and cats=portion is smooth muscles
-birds: entirely smooth muscle

29
Q

What are the 2 sphincters in the esophagus?

A

-upper esophageal sphincter (UES): crichopharyngeal muscle
-lower esophageal sphincter (LES)

30
Q

What are the functions of the esophagus and sphincters?

A

-movement of food from the mouth to the stomach
-protection of airway and esophagus

31
Q

What is the innervation of the straited muscle portions of the esophagus?

A

-somatic motor neurons in VAGUS nerve

32
Q

What is the innervation of the smooth muscle portion of the esophagus?

A

-enteric nervous system

33
Q

How is food propelled in the esophagus?

A

-by peristalsis
>propulsive movements
-ring of constrictions
*secondary peristaltic waves may be necessary

34
Q

What happens when the food reaches the distal end of the esophagus?

A

-LES relaxes
>ingested material enters the stomach

35
Q

What happens if the bolus is lodged in the esophagus?

A

-secondary peristaltic waves may lead to muscle spasms

36
Q

What happens to the UES and LES when not swallowing?

A

-remain constricted
-inspiration leads to pressure on the esophagus in the thorax
>if not constricted=aspiration of air from pharynx and ingesta from the stomach

37
Q

Swallowing and pressure:

A

-increases intrapharyngeal pressure due to reduction in volume of closed pharyngeal cavity (bolus in a small area)
>results in sudden relaxation of pharyngeoesophageal junction
>helps push bolus through
*without pressure=sphincter is closed
-sphincter will then close to prevent backflow=pressure increases

38
Q

What is the relaxation of LES mediated by?

A

-vasoactive intestinal polypeptide (VIP)

39
Q

Vasoactive intestinal polypeptide (VIP):

A

-neuropeptide produced by ENS neurons in response to bolus of food

40
Q

In most species the opening of the lower esophageal sphincter is accompanied by:

A

-a peristaltic wave within the esophagus
>pushes food into the stomach
»stomach muscles are relaxed=reducing pressure in stomach=material not ejected back into esophagus

41
Q

Distension of the stomach affects:

A

-meal size
>some carnivores have very distensible stomachs
>horse=small stomach=little distension

42
Q

Gastro-esophageal reflux disease (GERD):

A

-pathological reflux of gastric or duodenal contents
>leads to esophageal complications

MONOGASTRIC GI (24 decks)

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